Body fluid homeostasis Flashcards
What is the anti diuretic hormone?
Vasopressin
Where is vasopressin released from?
Posterior pituitary gland
Where is vasopressin produced? By what?
Produced in the hypothalamus by neurosecretory neurons
What is the trigger for a release in vasopressin?
An increase in osmolality
Where is the main place in the hypothalamus that vasopressin can be found?
The supra-optic nucleus
What are the 2 hypothalamic osmoreceptors?
Supra-optic nucleus
Paraventricular nucleus
What stimulates the hypothalamic osmoreceptors?
An increase in osmolality
Which substances promotes the release of vasopressin?
Nicotine
Ecstasy
What substance inhibits the release of vasopressin?
Alcohol
Why can overuse of ecstasy cause death?
Ecstasy promotes the release of vasopressin ->
Body will retain water which is normally secreted ->
Brain oedema due to overload of fluid
Where is the V2 receptor found?
Principal cell
Describe the vasopressin binding to V2 cascade
Vasopressin binds to V2
->
Activates PKA to phosphorylate vesicles underneath apical membrane
->
Water channels fuse with apical membrane and AQP2 increases
What is the net effect of vasopressin binding to V2 receptors?
Increase in water absorption
Decrease in body fluid osmolality
How does diabetes insipidus affect vasopressin release?
There is no release of vasopressin (central DI)
Vasopressin is released but is ineffective (nephrogenic DI)
Where is aldosterone released from?
Zona glomerulosa layer of the cortex of the adrenal gland
What is the role of mineralocorticoids?
Regulates plasma sodium, potassium
Regulates ECF volume
How do mineralocorticoids regulate ecf volume?
Via renin angiotensin
What does aldosterone act on?
The late distal tubule
Collecting duct
What is the cascade of events after aldosterone enters the principal cell?
Aldosterone binds to mineralocorticoid
->
The aldoMR complex stimulates RNA transcription and protein synthesis
->
This promotes opening of Na+ channels, promoting Na+ reabsorption
->
K+ and H+ are secreted
What is NPO?
Number of open sodium channel
What si the relationship between aldosterone and NPO?
NPO increases as aldosterone increases
What happens in an alpha intercalated cell after aldosterone enters?
RNA transcription
Protein synthesis
H+ secretion
What is pseudohypoaldosteronism caused by?
Mutations in the mineralocorticoid receptor
What does renin angiotensin regulate?
Body fluid volume
Plasma Na+ & K+
Where is renin released from?
Juxtaglomerular apparatus (JGA)
What is the renin - angiotensin cascade?
When ecf volume decreases, JGA releases renin
->
Renin converts angiotensinogen to angiotensin 1
->
ACE converts angiotensin 1 to angiotensin 2
What is the net effect of angiotensin 2?
Increase in Na+, ECFV and Bp
What happens when salt is ingested?
Aldosterone is inhibited and Vasopressin is activated
